Ah, it works. It is really chunked sequences. Thanks. Having been using clojure for half a year, it keeps really bringing me surprise and fun :)
2013/3/17 Marko Topolnik <[email protected]> > This is one of the most frequenly-asked questions and a source of surprise > to practically every new Clojure user. An update to the official > documentation on lazy sequences would surely help a lot here. > > -marko > > > On Sunday, March 17, 2013 9:18:05 AM UTC+1, Evan Mezeske wrote: >> >> I'd guess that what you're seeing is related to chunked sequences: >> http://blog.fogus.**me/2010/01/22/de-chunkifying-**sequences-in-clojure/<http://blog.fogus.me/2010/01/22/de-chunkifying-sequences-in-clojure/>. >> >> On Sunday, March 17, 2013 1:12:17 AM UTC-7, bruce li wrote: >>> >>> Hello, everyone. I'm writing some code that utilizes the lazy sequence. >>> But I found something strange. Here is how: >>> >>> The code is like: >>> >>> (first (filter some-expensive-io urls)) >>> >>> The code is aimed to find the first result of the operations on the urls >>> that is not nil. However, it seems that the io operations are executed once >>> more than needed. As the operations are slow, one more round increases the >>> overhead dramatically. >>> >>> Then I tested other pieces of code, such as: >>> >>> (first (filter #(when (> % 1) (println %) %) (range))) >>> >>> It prints out: >>> 2 >>> 3 >>> 4 >>> 5 >>> 6 >>> 7 >>> 8 >>> 9 >>> 10 >>> 11 >>> 12 >>> 13 >>> 14 >>> 15 >>> 16 >>> 17 >>> 18 >>> 19 >>> 20 >>> 21 >>> 22 >>> 23 >>> 24 >>> 25 >>> 26 >>> 27 >>> 28 >>> 29 >>> 30 >>> 31 >>> >>> and returns: 2 >>> >>> So why the lazy sequence is realized more than it is needed? Could I >>> enforce the laziness and save unnecessary operation? >>> >>> >>> Thanks, >>> Bruce Li >>> >> -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to [email protected] > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to [email protected] Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
